How to append/link Screens from other blendfiles?
A screen layout created in one .blend file cannot be linked/appended (manually or with python) into another, because Blender does not support this.

With python you can create new screen layout (bpy.ops.screens.new()) and change it's areas how ever you like.

You can access data inside external .blend files and read them with Blender-file.

This can be turned into addon for ease of use.